Where a variety of different types or sizes of sensor may be connected to an imaging system it is very desirable to determine the number of pixels and lines of a connected sensor array to determine an appropriate clocking scheme. Preferably, not only a size of the array making up the sensor is determined, but also a type of the sensor is identified as a known sensor type, in order to apply, for example, predetermined optimal bias voltages and gain for an output signal. For example, in dental x-ray imaging, a dental surgeon may select one of say three x-ray sensors with differing numbers of pixels dependent, for example, on an area to be x-rayed or the size of a patient's oral cavity. At present, with a manual system, a dental surgeon has disadvantageously to divert his attention from a patient to key into a computer keyboard of an imaging system a type of sensor connected to the imaging system. It is preferable if the imaging system automatically identifies a type of sensor connected to the imaging system. It is known to use an EPROM in association with a sensor, for example connected in series in a connector to the sensor, to provide an identifying signal to an imaging system to identify the type, and possibly a serial number, of the sensor. However, use of an EPROM adds undesirable cost and complexity to the sensor and is dependent on recognition by the imaging system of the identifying signal.
It would also be desirable for an imaging system to be able to detect if a sensor connected to the imaging system has a major fault or to detect that no sensor array is connected.
Moreover, having determined an array size it is very desirable to be able to determine an actual identity of a connected sensor, particularly where more than one sensor of a given array size may be connected to an imaging system. For example, defect maps are typically provided with each sensor, indicating locations of atypical pixels so that readings from the atypical pixels can be corrected and it is necessary to know which sensor is connected in order to use a corresponding defect map. Thus, for example, U.S. Pat. No. 6,618,084-B1 discloses a method of determining the location of defective pixels in a sensor array, storing these locations in a memory associated with the sensor, for example on the same chip as a CMOS sensor, and making corrections for readings, or a lack of a reading, from defective pixels. In circumstances where a plurality of sensors may be connected to an imaging system, it is advantageous instead to store maps of the defects centrally, either in the imaging system or in a central database accessible remotely, and to identify the sensor connected to the imaging system so that a corresponding defect map may be used to correct an image generated by the connected sensor. It is preferable if the imaging system automatically identifies a sensor connected to the imaging system. It is known to use an EEPROM in association with a sensor, for example in series in a connector to the sensor, to provide an identifying signal to an imaging system to identify the sensor. However, use of an EEPROM adds undesirable cost and complexity to the sensor and is dependent on recognition by the imaging system of the identifying signal.
In summary, a known method of improving quality of a CCD image comprises storage of dark and bright/flat field image data, and the correction of dark and bright defects in subsequent images by appropriate processing using the stored data. In order to do this, known CCD drive or imaging systems either require: a fixed, single CCD array sensor with only one corresponding set of stored dark and flat field image data, manual selection of a particular CCD serial number, from a set of serial numbers, in order to retrieve the appropriate dark and flat field data or automatic selection of a particular CCD serial number by reading an EEPROM incorporated into a CCD connector, in order to retrieve the appropriate dark and flat field data.
It would be advantageous to be able to identify a sensor uniquely and automatically from a set of sensors to apply corrections, without the use of a EEPROM.
It would also be advantageous to be able to identify a sensor uniquely for warranty purposes, for example, to determine whether a particular sensor is covered by a particular manufacturer's or supplier's warranty.